And fireproofing wood and other materials



UNIT D s'r rEs PATENT OFFICE- ARTHUR AREN'T, or BADGER, AND RUDOLPH A. KUEvER, OF IowA crrY, IowA, Assm ons, BY manor AND MESNE ASSIGNMENTS, T0 ARENTOX COMPANY, OF CHICA O, ILLINoIs, A CORPORATION 01 DELAWARE.

ART OI PROTECTING- AND 'FIREPROOFING WOOD AND OTHER MATERIALS.

Specification of Letters Patent.

Patented Oct. 14,1919.

No'Drawing; Application filed April 28, 1916, Serial No. 94,245. Itenewed February 21, 1919. Serial No.

To all whom it may concern.

Be it known that we, ARTHUR ARENT and :RUDOLPH A. KUEVER, citizens of the United States, residing at Badger, in the county of Webster and State of Iowa, and Iowa City, in the county of Johnson and State of Iowa, respectively, have invented certain new and useful Improvements in the'Art of Protecting and Fireproofing Wood and other Materials; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the art of protecting and fireproofing wood and other materials; and it comprises a process in which wood, cloth, or other material to be fire proofed and protected against weather con ditions, etc, is treated with asolution ofa zinc'compound of such character: as to penetrate the material readily and to deposit therein a substantially insoluble compound of zinc without the aid of an auxiliary zinc precipitant. I

The invention also comprises the treated product resulting from said process, as well as the treating solution employed therein.

It has been proposed heretofore to employ solutionsof zinc salts, such as the chlorid and the sulfate, for fireproofing wood; but in these prior methods such of the zinc salt as is retained. by the wood remains in soluble condition unless precipitated on the fiber by a second step of impregnation with a zinc precipitant.

An object of the present invention is to permanently fireproof and preserve mate rials of various kinds by a simple one-step impregnation process which can be carried out in practice with maximum convenienceand at lowv cost. More particularly the invention contemplates impregnating or otherwise suitably treating materials with a zinccontaining solution of relatively high zinc content of such character that upon evaporation it will give a deposit of zinc oxid or an oxy-salt of zinc, or'both, in the pores or on the fiber of the material, substantially,

no non-volatilizable matter, other than said zinc oxid or oxy-salt, being added to the wood by the treatment.

In the best form of the invention at present known to us, the treating solution is aqueous and is characterized by an alkaline reaction. This is in contradistinction to the ordinary aqueous treating solutionof zinc chlorid, for example, which is somewhat acid in reaction, due to the fact that it is a salt of a strong acid and a weak base. Furthermore, in our treating solution as employed in practice, the zinc is most desirably present, at least in part, as a compound resulting from reaction between zinc chlorid and ammonium hydroxid. This compound acts like, and probably is, an ammonium zincate. It is rather readily decomposed either upon spontaneous evaporation or upon moderate heating, with formation of in soluble zinc oxid. The solution may also advantageously contain zinc in the form of a compound which upon evaporation, especially in the presence of a base such as ammonium hydroxid, will yield an insoluble basic salt or'salts of zinc. In practice,'a compound resulting from reaction between zinc chlorid and ammonium chlorid, probably in the nature of a double chlorid, is found to be highly useful for this purpose and is employed in conjunction with the first mentioned compound in somewhat ammoniacal aqueous solution.

For the purposes of this invention a solution such as that above described has special advantages in that the solution, upon evaporation, yields a mixture of insoluble zinc oxid and oxychlorids, or other basic salts.

In order to explain clearly the principles of the invention, a practical method of carrying it into effect will be described in detail. It i to be borne in mind, however, that this specific example is merely illustrative and that the ingredients, their proporbe neutralized by stirring an excess of Zinc carbonate into the solution and filtering through mineral wool, the undissolved zinc carbonate cooperating with the mineral wool to provide an eflicient filtering bed. This procedure is especially advantageous where the starting materials are relatively impure. In 300 liters of the zinc chlorid solution are dissolved 20 kilos of ammonium chlorid at ordinary temperature, and to. the mixture are addedgradually and with' constant stirring, 350 liters of ammonium hydroxid (28 per cent. NH the stirring being best continued until the solution has cooled from the temperature developed in the reaction to about 30 C. During the stirring sufiicient water, about 340 liters, is added to make about 1000 liters of the solution at 30 C.

Such a solution contains zinc, ammonium,

and acid radicals or groups, and from sim ple calculations based on the data given, it will be seen that the amomnium radical is present in substantial excess over the proportion required to satisfy the acid radical, or the acid radicals where more than one acid is employed. The resultant alkalinity of the solution is such as to give a distinct basic reaction withphenolphthalein as Well as with litmus. This condition is an important characteristic .of our fireproofing solution in its inost desirable form and it is due to thisfact that the zinc' is directly deposited as oxid or an oxysalt upon evaporation of the solution. K

At 25 C. the solution has a s ity of 1.15, and when dilute with four volumes of water it precipitates a dense,'voluminous, flocculent precipitate of zinc hydroxid and basic zinc *chlorids. It contai ns substantially 10 per cent. of combined. metallic zinc. deposits the greater part of its zinc content as zinc oxid mixed with variable amounts of basic zinc chlorids or oxychlorids, the proportion of the latter depending largely upon the rapidity of evaporation.

It is to be understood that the proportions of the reagents used can be varied considerably within the scope of the invention, but the content of combined zinc in the treating solution should amount to several per cent, by weight, ordinarily not less than about 5 per cent. The proportions recited in the above specific example have been found especially advantageous practically, however, because they give asolution of large zinc content and relatively low ammonium salt content. The presbnce of the ammonium salt enables the solution to hold much more zinc than it could otherwise; but toolarge an amount of the ammonium salt is undesirable. I I

The solution, prepared as described, is

Upon evaporation, the solution dipping, spraying, or any other method which will insure the requlsite degree; of impregnation By reason of its freedom from mucilaginous and gummy constituents, the solution is highly fluid or penetrating in character, in spite of its hi h content of combined zinc. In fireproo g wood, for egample, combined vacuum and pressure" treatment similar to that used in creosoting wood, may be effectively employed. Drying of the treated materials may or may not i be hastened by application of heat. If rapid drying is resorted to, it should be carried out in a suitable drying chamber from which any ammonia and ammonium chlorid volatilized in the operation may be led away and recovered in well known-ways for re-use.

While we do not desire to be limited to any particular theory as to what actually occurs in preparing the fireproofing solution. or its conduct upon evaporation, as de scribed in the foregoing specific example, it is probable that the general character of the reactions can be explained With approximate accuracy as follows:

Addition of ammonium chlorid to the zinc chlorid solution gives a double salt zinc and ammonium. This takes care of only a comparatively small proportion of the zinc chlorid present, however, the rest of the zinc "chlorid forming, with the added ammonium like zincates, such as ammonlum orthozincate and perhaps some metazincate. In the example given a slight excess of ammonia is used so that the finished solution has a. distinctly basic reaction toward phenolphthalein as well as toward litmus and a characteristic faintly ammoniacal odor.

Upon evaporation of the water from the impregnated wood or the like, the ammonium zincates, or the compounds resembling zincates in conduct, break up, depositing insoluble zinc oxid and settingfree ammonia and water. At thesame time the double salt of zinc and ammonium decomposes into its constituent chlorids, and the zinc chlorid, reacting with the ammonium hydroxid present, yields more or less complex mixtures of insoluble basic chlorids such as Zn,0C1 -ZnOHC1, etc.

The advantages attained in the practice of this invention are important. Wood, for

example, thoroughly saturated with this solution and dried retains within its pores a large amount of zinc oxid'and some basic zinc chlorids, all of which are substantially insoluble in water and which therefore remain in the wood permanently even though it be exposed'to severe weather conditions.

The wood is uninflammable, merely charring slowly upon exposure to direct flame, If,

- left in the wood by the treatment. Onthe other hand, if the wood is simply air dried, any persisting ammonium compounds constitute-in themselves valuable fireproofing agents.

It is to be noted that although, in accordance with our process, a large percentage of zinc ininsoluble form can be deposited in material to be protected, this .is done without deleterious effect upon the fiber of the material; If it be attempted to treat wood or other cellulosic material with a zinc'chlorid solution of a zinc content'as high as that of the present treating solution, the'fibers are thereby weakened, while in addition the residue left in the wood by a zinc chlorid so lution is hygroscopic, a disadvantage which is overcome with our solution.

While the chlorids of zinc and ammonium are specified in the example given. above, other salts may be used, although for most purposes they offer no advantageover the chlorids and are ordinarily less suitable. It is particularly .desirable, however, that whatever acid radical is employed shall be volatilizable upon moderate heating. Thus the sulfate of zinc, though less advanta: geous, will serve instead of the chlorid;

while the bromid, iodid, sulfate, etc., of

ammonium may replace sal ammoniac.

What we claim is: 1. The process of protecting materials and decreasing their combustibility, which comprises treating such a material with an am- -moniacal solution containing a zinc compound but substantially free of other nonvolatile constituents, said solution having an alkaline reaction toward phenolphthalein and its content of combined zinc being at least about 5 per cent.

2. The process of protecting materials and decreasing their combustibility which comprises treating such a material with a highly fluid ammoniacal solution of a zinc compound, said solution being alkaline to phe nolphthalein, and containing several per cent. of zinc but being substantially .free of other non-volatile constituents.

. of said solution amounting 3. The process of protecting materials and decreasing their combustibility which comprises treating such a material with an aqueous solution containing a zinc and am monium' compound and. ammonium hydroxid, said solution being alkaline to phenolph'thalein,. and drying the treated material to deposit a water-insoluble zinc com pound therein or thereon, the zinc content cent. 4. Theprocess of protecting materials and decreasmgthelr combustibility which com- 5. The process of protecting materials and decreasing their combustibility which com prises treating such a material with an alkaline solution containing an ammonlum zincate and a salt of zinc, the zinc content 1 of the solution being relatively high.

6. The process of protecting materials and decreasing their combustibility which comprises treating such a material with an alkaline solution containing an ammonium zincate, a salt of zinc, and another ammonium salt.

7 The process of protecting materials and decreasing their combustibility whichcomprises treating such a material with an alkaline solution containing an ammonium zincate, zinc chlorid and ammonium chlorid.

8. The process of fireproofing wood which comprises impregnating wood with an alkaline-to-phenolphthalein solution of a zinc compound, the zinc content of the solution amounting to several per cent., drying the wood and thereby depositing within the wood waterinsoluble zinc compound having fire-retarding properties. a

9. The process of fireproofing wood whlch comprises impregnating wood with an alkalineto-phenolphthalein ammoniacal solution of a heavy metal compound,'the metal content of the solution amounting to at least about 5 per cent., drying the wood and there by depositing within the wood a water-insoluble heavy metal compound having fire-retarding properties;

- 10. The process of treating wood and the like which comprises impregnating wood or other material with a solution containing a zinc compound and an ammonium compound and having antalkaline reaction toward phenolphthaleln, the zinc content of the solution amounting to at least about 5 per cent. 11. The process of protecting materials and decreasing their combustibility which comprises treating such a material with an alkaline solution containing zinc, ammos nium, and acid radicals, the proportion of the ammonium radical present being in substantial excess of that required to satisfy said acid radical or radicals and the content of combined zinc amounting to several per cent. r

12. The process of protectively treating fibrous material which comprises impregnat ing such material with an ammomacal aqueous solution containing approximately ten per cent. of'combined'zinc and drying to several per the treated material.

13. The process of protectively treating fibrous material which comprises impregnating such material with an aqueous solution containing a zinc compound and an ammonium compound, said solution containing approximately ten per cent.- of combined mm, and drying the treated material.

14. As anew article of manufacture, fireproofed or uninfiammable material cont-aim mg distributed therethrough a non-hygroseopiemlxture of zinc oxid and a zinc oXy-salt of a relatively volatile acid radical, said material being substantially free of added Water-soluble non-volatilizable compounds.

15. As a new article of manufacture, fireproofed or uninfiammable material containing distributed therethrough a non-hy roscopie mixture of zinc oxid and a basic c 10- rid of zinc, said material being substantially free of added water-soluble non-volatilizable compounds.

In testimony whereof we hereunto aifix our signatures.

, ARTHUR ARENT.

RUDOLPH A. KUEVER. 

